The present invention relates to measurement and location systems and, more particulary, to a triaxis laser system useful for providing measurable angular information with respect to a ground plane.
Laser systems designed for a multitude of purposes have been generally commercially available since the 1960's. Basic refinements in these systems have included bulk reductions and the advent of the low power laser (with an output of the order of several milliwatts). With the compacting of laser technology, the number of practical laser applications have been compounded.
As compared to other conventional alignment techniques, the advantages of laser systems include increased sensitivity, faster recording of measurements and remote meter readout. These and other advantages have combined to provide impetus to an increasing trend toward the commercial use of lasers. In the field of manufacturing alignment techniques, laser devices are firmly embedded for applications such as aligning avionic systems on sophisticated aircraft. In this environment, the increased accuracy, decreased time required for alignment and the decrease in the necessary operator skill level all provide further incentives for employment of laser technology.
Previous laser alignment systems have recognized that the coherent laser beam could be directed towards an angularly adjustable reflective surface from which it would be reflected to a fixed target. Typically, the incident beam passes through an aperture at the center of the target, and by manipulation of the reflective surface, the returning beam can be relocated as to strike the target at approximately the target center. This indicates that the reflective surface is now oriented perfectly, or nearly perfectly, perpendicular to the plane of the laser.
Various modifications of this technique have since been proposed, all of which share the common aim of producing an optical alignment system which senses an angular displacement. Most have means of reorienting some component as to produce a null, representing the desired alignment. While systems of this general type have been satisfactory for various alignment applications, they fail to provide apparatus which is capable of actually measuring the angular displacement of the moving body. The ability to make such measurements and to define planes at a discrete angle from a given reference is essential for various manufacturing techniques as well as for surveying and other grading applications.
One reference pertaining to a type of optical measuring system is disclosed in U.S. Pat. No. 3,269,254, issued to L. Cooper, et al. This device includes a graded mirror to define the roll, pitch and yaw orientation of a body to which the mirror is attached. The patentees use an autocollimation system to project the graded light pattern upon an image measuring reticle. A linear scale can be imposed upon the reticle for measuring angular displacement of the body. This scale is determinable based upon the distance of the collimating lens from the reticle and the focal length of the lens.
A fundamental problem with this type of configuration is that the collimator lens must be located close enough to the moveable body to receive enough light rays to produce a discernable pattern at the reticle. The light source and reticle must also be displaced from the lens a distance no greater than its own focal length.
These and other inherent limitations restrict the Cooper system to a range of operation of about one to two feet (between the moveable body and imaging target) and to use with other than laser light sources. These are impractical limitations for the type of applications for which the present invention was intended. Nowhere has it been proposed that a purely optical system may be employed to actually measure the degree of relative angular displacement between surfaces, in three axis, irrespective of the distance between the reference source and target.
It is, therefore, a major purpose of this invention to provide a laser measurement system which not only senses misalignment between a plurality of surfaces, but also allows for the accurate angular measurement of such displacement in three axis completely independent of a ground reference.
It is a general purpose of the present invention to provide a family of optical alignment techniques which eliminate any requirement for an ocular lens system, imaging focusing lenses or image measuring reticles in initial system alignment or subsequent measurement of the relative angular displacement between the various surfaces.